Dead Man's Bluff
ded mans bluhf–noun
1.
a cliff, headland, or hill with a broad, steep face where people go to die. (also a clump or grove of trees on a prairie or other generally treeless area.)
2.
when someone calls out the (typically but not necessarily fatal) bluff of another person (typically a 'Suicidal, Clinically Depressed' individual)... in an attempt to taunt that person (via psychological deception) to 'come clean' with the truth - dropping the perceived allegation, bluff or charade.... and:
Develops when the believed-to-be-fibber FOLLOWS THROUGH on the taunt, culminating in (either: a failed suicidal attempt, or) the taking of his or her own life.
(Note: should the taunt result in a tragic mishap; such as poisoning, dismemberment, or other (permanent) physical or psychological impairment; "Dead Man's Bluff" is applicable.
3.
situation whereby an otherwise reasonable assumption would result in death; an act of desperation Hail Mary to Remedy the matter is attempted as a last resort.

a "Dead Man's Bluff" is:
(1)
A beautiful countryside with overlooking cliffs designed as a graveyard, OR, the same where one would go to 'expire' upon imminent death.
(2)*
A modern example would be someone standing on a ledge with the apparent intent to jump to their death:
A 'good samaritan' goes to the ledge but - after the person fails to respond to 'Positive Reinforcement' - the samaritan tries using Reverse Psychology; resulting in the Disturbed individual to reflect more on the reasons TO jump.
Or, in any case, where the samaritan simply calls on the jumper to carry out the 'threat' 'Suicide Angel', resulting in a Failed attempt in reverse psychology, where the jumper's resolve is solidified to fulfill the act.
(3)
If someone were to fall into the hands of an enemy; and that enemy were threatening to Kill that man (whereby death was imminent) - the man would declare intimate knowledge of something of value to his captors to sustain his own life for an extended period of time.